Lenticular imaging is a method known to those skilled in the art to compose a series of multiple images or frames onto the focal plan of an array of lenticular lenses so when a viewer views the image through the array of lenses from a particular distance and angle, the viewer will only see one of the multiple images or frames behind the array of lenses. This method is used to form applications such as but not limited to animation transition of images that occurs when a viewer of the lenticular image alters their viewing angle. The method creates the ability for a viewer to view different images from different angles on a printed media having multiple images behind a lenticular sheet which is known for creating autosteroscopic images for a pair of eyes having a small differential between the viewing angle of each eye. A three-dimensional image using lenticular arrays under this principle is, also known as stereoscopic printing. Stereoscopic prints utilize a process that employs a plurality of lenticular lenses to permit the viewer of the image to perceive the image stereoscopically. This type of image is routinely used to make posters or advertisement prints more conspicuous to the viewer, most often for the purpose of promoting a product or service. Traditional lenticular prints are produced by dividing images of the same object that have been acquired at different angles into vertical strips and arraying the strips onto the back of lenticular lenses, or a printing substrate, such that the strips are positioned in general axial alignment with the half-cylindrical shape of the lenticular lenses.
There are many problems with the current technology that is utilized to create a lenticular print. Currently, multiple frames are captured of the same object and are combined into vertical strips to create a composite image using a process called interlacing. Each vertical strip is aligned with a lenticular sheet having a plurality of lenticular elements such that the vertical strips of the composite image are substantially axially aligned with the lenticular elements. One problem with this current method is that the vertical strip pitch must be properly aligned with and precisely matching the lenticular sheet's lentical element pitch in order for the image to be synchronized over the range of lentical elements from a given viewing position. If the vertical strip pitch is misaligned with the lenticular sheet's lentical pitch an effect known to those skilled in the art as, ghosting, will occur. Ghosting occurs due to poor treatment of the source images, more specifically the improper matching of the physical parameters of frames viewing distance and viewing angles, and can further be attributed to transitions where demand for an effect goes beyond the limits and technical possibilities of the printer. This causes some of the images to remain visible when they should disappear. These negative effects can depend on numerous conditions such as, but not limited to, the lighting of the lenticular print or mismatch of vertical strip pitch and lentical pitch.
An additional shortcoming of the current technology of lenticular prints involves the horizontal printer pixel pitch. Currently in the printing industry, printers have a certain resolution specification also known as dot pitch or dot per inches. The horizontal printer dot pitch is a specification of the distance between the dot samples points of the same color for which a printer can natively print. To create a color image, multiple dots from different colorants form a group of dot arrangement pattern to represent a single image pixel. The native smallest pixel to pixel pitch is thus determined by the dot per inches of a given printer. Conventional printing technology utilizes a checker board image style pixel arrangement in an X-Y coordinate system. As previously mentioned herein, for a lenticular print, the frames utilized to create the interlaced image are vertically divided into strips. The amount of vertical strips are based on the number of half-cylindrical shaped lenses of the lenticular sheet to be utilized as well as the number of frame behind each lens element. The combination of the limitation of the horizontal printer pixel pitch,ppp, and the lens element pitch,lep, function to limit the angular resolution of the image by capping the maximum number of frames,mnf, that can be printed in a lenticular print with the relationship of mnf=<lep/ppp wherein mnf is typically not a natural number.
However, the requirement to synchronize across a wide range of lenticular lens elements for the printed group frame strip to match the lens element pitch from a given viewing distance is needed to prevent the ghosting problem but this requires that lep/ppp be a natural number. When attempting to synchronize spatially between two periodical functions with two unmatched pitches, wherein unmatched pitches occurs when one pitch is not a whole number multiplication of the other pitch, and the error will accumulate of a period of spatial width resulting in a need for correction. As is known in the art, two methods are employed to facilitate correction, first an adding/dropping method can be used and secondly an interpolation and re-sampling method is utilized. The adding/dropping method utilizes a repeat correction by either adding or dropping one or more elements from the small pitch group periodically when the error accumulates to over one pitch of the smaller pitch in two periodical functions in order to maintain in sync with larger pitch. One problem with this method is that the method inevitably creates a spatial banding effect causing a undesired visual disturbance.
Another method of attempting to reduce the spatial banding effect involves a method where an interpolation and re-sampling needs to be used so that an envelop function, which composed of multi-angle and multiple frames of images wherein the envelop function is normalized so that pitch is equal to lens element pitch will need to be interpolated and re-sampled with a different printing pitch, i.e. printing resolution. Unfortunately, this method will create significant artifacts and error when the corresponding number of frames utilized, or the lep/ppp mapping is not a significantly large number, which is common in the industry.
Current technology utilizes a calibration procedure to attempt to overcome this pitch mismatch problem when calibrating between a printer, printer pixel pitch and the lens element pitch. As is known in the art, a calibration is performed by printing a test pattern that consists of vertical strips with different horizontal pitches and then overlap the lenticular sheet to determine if the resulting pattern is homogeneous from a desired viewing distance. Using this process, the actual pixel per inch needed is calculated to produce a composite multi-frame pattern that will match the physical pitch of the half-cylindrical shaped lenses of the lentical sheet. This calibration procedure modifies the desired printout resolution to a resolution that is non-native to the printer's capability. When attempting to print a lenticular image using a pixel resolution that is non-native to the printer's physical pixel resolution it can cause the printing software or firmware to either re-sample the original composite multi-angle pattern by interpolation between pixels and/or perform periodic addition or subtraction of pixels. Both scenarios described will cause either degradation, distortion or a progressive misalignment that will repeatedly appear in the lenticular print as a band.
The application of lenticular print to create a three dimensional view of an object is traditionally limited by the number of views achievable utilizing a traditional interlaced strip method behind a lenticular element which causes an irregular transition effect from one viewing angle to an adjacent viewing angle.
Accordingly, there is a need to provide a method for producing a lenticular print overcomes the above shortcomings, including a method that substantially reduces the effects of ghosting and offers increased horizontal angular resolution of the final lenticular print.